Family Atlas v Rootsmagic 5's mapping facility

I have Rootsmagic 4 and am wondering whether to upgrade to Rootsmagic 5, or buy Family Atlas, or both. I understand that mapping software is included in Rootsmagic 5, but how does it compare to Family Atlas?

I am doing a One Name Study as well as my family history, so I like the ability on Family Atlas (having watched the webinar) to show several families/name variants at once, and the time slider.